The present invention relates to a memory system which uses slow access time memory elements as a main memory as represented by a magnetic bubble memory, and a method for access in such a memory system.
The magnetic bubble memory is of large capacity and the low cost and memory contents thereof are not destroyed when the power is shut off. Thus, the use of the magnetic bubble memory as a main memory for controlling an office machine or an industrial machine has been discussed. However, in spite of the advantages described above, the magnetic bubble memory has not been used as expected. The biggest cause therefor is that the access time of the magnetic bubble memory is several tens of milliseconds which is very slow in comparison with the access time of a core memory or a semiconductor memory, which is 100 microseconds.
Accordingly, the magnetic bubble memory is not suitable for use with a high performance robot or a high performance machine tool which requires access to the main memory at a high frequency, and the application of the large capacity memory is limited when it is not applicable to the high performance robot or the high performance machine tool.